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Biomedical subjects

D C Walker

Publications and source records attributed to D C Walker.

At least 55 records · Page 3Linked to original sources
PubMed1989

Respiratory epithelial permeability after cigarette smoke exposure in guinea pigs.

The purpose of this study was to determine the pathology of cigarette smoke-increased permeability at the bronchioalveolar junction of the guinea pig. After exposure to either smoke or room air, guinea pigs were anesthetized and fluorescein isothiocyanate-dextran (FITC-D, mol wt 10,000) was aerosolized into their lungs. Blood samples taken through a carotid arterial cannula were analyzed by gel chromatography and spectrofluorometry for the presence of FITC-D. The results confirmed that, after smoke exposure, increased amounts of intact FITC-D molecules with a reported Einstein-Stokes radius of 22.2 A crossed the respiratory epithelium into the vascular space. Transmission electron-microscopic studies showed that the FITC-D diffused across damaged type I pneumocyte membranes and cytoplasm to reach the basal lamina and entered the alveolar capillaries through endothelial tight junctions. Damage to the alveolar epithelium was more frequent for the smoke-exposed animals than the room air-exposed animals (P less than 0.05). We conclude that smoke exposure damages type I cells and that inhaled FITC-D crosses the epithelial barrier at damaged type I cells of the bronchioloalveolar junctions.

Aerosols↗
PubMed1988

Histochemical studies of the colonic epithelial glycoproteins of the normal rabbit.

Two general classes of glycoproteins have been identified in the colonic epithelial cells of New Zealand white rabbits. Each is associated with an ultrastructurally distinct secretory cell. The first of these classes is found in cells, termed vesiculated columnar cells, characterized by electron-translucent vesicles, a small rough endoplasmic reticulum-Golgi complex and prominent microvilli. The glycoproteins of the vesiculated cells contain abundant O-sulphate ester, sialic acids with ester substituents at positions C-8 or C-9 (or with two or three side chain substituents) and neutral sugars with vicinal diols whose periodate oxidation is prevented by an O-acyl ester substituent(s). The second class of glycoproteins occurs in goblet cells characterized by electron-dense vesicles, an abundant rough endoplasmic reticulum, a well-developed Golgi apparatus and few, if any, microvilli. Goblet cells along the entire length of the crypts contain neutral sugars with periodate-oxidisable vicinal diols and a ferriferricyanide-reactive component. Cells in the upper halves of the crypts also contain components that are sulphated, Schiff-reactive and acid-fast. In the lower halves of the crypts, the goblet cells contain smaller quantities of the above components plus sialic acids, some of which possibly have an O-acyl substituent located at position C-8 or C-9 (or which have two or three side chain O-acyl substituents). It is suggested that the function of the glycoproteins from the vesiculated columnar cells is protective and that from the goblet cells is lubricative.

Animals↗
PubMed1988

Physiologic and histologic determinants of gas exchange during induction of oleic acid pulmonary edema.

Five anesthetized mongrel dogs were studied during the induction of acute oleic acid pulmonary edema to determine the influence of cardiac output (Qt), extravascular lung water (ETV), and the degree of alveolar flooding on pulmonary gas exchange. Ot and ETV were measured by thermal dye dilution techniques, alveolar flooding was assesed by histologic studies, and gas exchange was quantitated by the multiple inert gas elimination technique (MIGET). Estimates of the inert gas venous admixture [(Qva/ Qt) IG%] were obtained at different experimental stages from the MIGET data to provide an index of overall gas exchange impairment. Pulmonary edema was produced by the intravenous (IV) infusion of oleic acid (0.08 mL/kg). Measurements of Qt, ETV and (Qva/Qt) IG% were made prior to lung injury and at 40, 80, and 120 minutes after injury. After death the lungs were inflated and frozen. Thirty cores of lung parenchyma (2 mL each) were obtained for histologic assessment of alveolar flooding. In the early phase of edema formation (0 to 80 minutes), (Ova/Qt) IG% increased as ETV increased. After 80 minutes, ETV stabilized and further changes in (Qva/ Qt) IG% were then primarily determined by changes in Qt (r = .94). The histologically assessed degree of alveolar flooding correlated well with ETV at the 120-minutes stage (r = .85). However, by use of multivariate analysis, the addition of the histologic information did not appreciably improve the prediction of gas exchange in acute oleic acid pulmonary edema.

Animals↗
PubMed1988

Effects of high voltage pulsed electrical stimulation on blood flow.

The purpose of this study was to determine whether high voltage electrical stimulation would increase blood flow to skeletal muscle in healthy subjects. Subjects were assigned to one of three groups: 1) an Electrical Stimulation (ES) Group (n = 16), 2) an Exercise (EX) Group (n = 14), or 3) a Control Group (n = 8). Isometric contractions were induced electrically at 30 Hz in the ES Group and performed volitionally in the EX Group for five minutes at intensities of 10% and 30% of predetermined maximal voluntary isometric contraction (MVC) efforts. Blood flow, heart rate, and blood pressure were unaffected in the ES Group, but blood flow and systolic blood pressure increased and decreased, respectively, for the EX Group at 30% of MVC. High voltage stimulation at a pulse rate of 30 Hz and at intensities needed to evoke contractions at 10% and 30% of MVC for plantar flexion did not increase blood flow at the popliteal artery.

Adult↗
PubMed1988

Assessment of tight junctions between pulmonary epithelial and endothelial cells.

This study is intended to determine whether qualitative assessment of tight junction integrity from freeze-fracture data is reliable. We used lung parenchyma from a control mongrel dog's cardiac lung lobe, from a mongrel dog subjected to vascular high-pressure pulmonary edema (HPPE), and from a dog subjected to oleic acid-induced low-pressure pulmonary edema (LPPE) (6). Quantitative assessment was done on 115 freeze-fracture micrographs of epithelial tight junctions and on another 158 freeze-fracture micrographs of endothelial junctions from the 3 dogs. Quantitative assessment showed differences between the dogs in junction depth, fibril numbers, density, and complexity. for qualitative assessment, these same 273 micrographs were assessed in a single-blind fashion by having six investigators sort first the epithelial and then the endothelial junctions into normal or damaged categories. Qualitative assessment did not agree with quantitative data, suggesting that it is unreliable.

Animals↗
PubMed1987

Effect of urethan anesthesia on cigarette smoke-induced airway injury in guinea pigs.

The effect of urethan anesthesia on cigarette smoke-induced airway responsiveness and permeability was studied in the guinea pig. Airway responsiveness was determined by measuring changes to airway resistance to graded doses of aerosolized histamine, and mucosal permeability was determined by measuring the appearance of fluorescein isothiocyanate-dextran (FITC-D) in the blood and examining its distribution in lung tissue after it had been delivered to the lung in an aerosol. The results confirm previous studies that smoke exposure increased airway responsiveness and mucosal permeability. They also show that urethan anesthesia administered before smoke exposure prevented the smoke-related changes in airway reactivity and mucosal permeability. In animals that remained conscious during the smoke exposure, there was increased deposition of the dextran in the regions of the bronchioloalveolar junctions with a more rapid uptake of FITC-D into the blood. We postulate that, when urethan anesthesia is administered before smoke exposure, the exudative phase of the inflammatory reaction produced by smoke exposure is suppressed.

Anesthesia, General↗
PubMed1986

Effect of breathing dry air on structure and function of airways.

We compared the effect of breathing dry air (0.70 mg H2O/l) with that of breathing room air (8.62 mg H2O/l) in guinea pigs anesthetized with urethane. The data showed that breathing dry air caused a reduction of extravascular water (EVW) in the trachea (P less than 0.01) but not the lung. Structural analysis showed that this water loss occurred from the loose connective tissue of the submucosa. Histamine dose response curves performed on the animals showed that breathing dry air caused an increase in the maximum response (delta max RL) (P less than 0.01) without changing either the dose required to produce 50% of the delta max RL or the ratio of delta max RL to this dose. We conclude that breathing dry air produces an acute reduction of EVW of the loose connective tissue of the airways and an increase in the maximum response to histamine.

Animals↗
PubMed1986

Alveolar epithelial damage. A critical difference between high pressure and oleic acid-induced low pressure pulmonary edema.

The present study was designed to compare high pressure pulmonary edema (HPPE) and oleic acid-induced low pressure pulmonary edema (OAPE) in dogs when similar amounts of extra vascular water were present in the lung. The high pressure edema was produced by intravenous fluid overload and by inflating an aortic balloon catheter (n = 6). The low pressure edema was produced by the injecting 0.08 mg/kg oleic acid suspended in 5 ml saline (n = 6). Comparison of the difference between initial control measurements and final measurements in the edematous states showed that the animals with OAPE had a greater fall in percent oxygen saturation and a greater increase in shunt fractions. The light microscopic studies showed that OAPE was associated with greater amounts of alveolar flooding than HPPE where the edema fluid was located to a greater extent in the peribronchial interstitial space. The electron microscopy studies showed that the alveolar flooding in OAPE was associated with epithelial disruption, and tracer studies carried out in rabbits showed that dextran (150,000 mol wt) could pass from blood to airspace and that dextran (40,000 mol wt) could pass from air-space to blood in OAPE. We conclude that epithelial disruption is responsible for the excessive alveolar flooding in OAPE and that this results in a greater impairment in gas exchange.

Animals↗
PubMed1985

Antioxidant enzyme content of pulmonary artery endothelial cells: effects of subculture.

The activities of glutathione peroxidase, superoxide dismutase and catalase, enzymes which play a critical role in protection of the vascular endothelium from oxygen free-radical injury, were determined in large vessel endothelial cells obtained under three different growth conditions: from freshly isolated from bovine pulmonary arteries, in the first (primary) subculture and after six serial subcultures (6.5 population doublings). The endothelium was obtained by mechanically scraping the vascular lumen. Endothelial cell monolayers were detached mechanically from the substratum prior to passage. No proteolytic enzymes were used in either procedure. The activities of catalase, superoxide dismutase and glutathione peroxidase determined in freshly isolated endothelial cells were, respectively, 39.9 +/- 10.3, 2.2 +/- 0.8 and 3.0 +/- 0.5 X 10(2) units per mg protein. After primary culture there was no change in superoxide dismutase activity, but a significant decrease in glutathione peroxidase activity to 1.4 +/- 0.4 X 10(2) was observed, and catalase activity dropped significantly to 18.6 +/- 5.0 units per mg protein. After 6.5 population doublings, the activity of all three enzymes returned to values similar to those of the freshly isolated cells. A fourfold increase in the protein to DNA ratio occurred in cells in primary culture and was maintained in sixth-passage cells. This increase in endothelial cell size upon culture was reflected in the electron microscopic evidence of cellular hypertrophy. Measurement of the rate of transport of 5-hydroxytryptamine by endothelial cell monolayers revealed a substantial loss upon multiple passage. Transport in the sixth-passage cells was decreased to one-half the rate of primary cells.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1985

A re-assessment of the tricellular region of epithelial cell tight junctions in trachea of guinea pig.

The tricellular region of epithelial tight junctions was previously dismissed as a possible avenue of permeability. One reason was that the two parallel vertical fibers, which penetrate the depth of the tight junction, were apparently cross-linked. Another reason was that the tricellular region of the tight junction is deeper than the adjacent bicellular regions. In the course of several freeze-fracture studies of epithelial tight junctions we have made observations which led us to re-assess the tricellular region as an avenue of permeability. We believe that information from ectoplasmic fracture faces is less subject to artifacts and, in ectoplasmic fracture faces of tricellular regions, cross-linking of the vertical furrows has not been observed. In guinea pig tracheal epithelium the tricellular junction is only about 1 micron deep. Following exposure to cigarette smoke, lanthanum ion staining has been observed in some tricellular junctions. It seems that earlier reasons for dismissing tricellular regions of the tight junction as permeability sites may be insufficient and that there is some evidence to support a role in permeability.

Animals↗
PubMed1985

Macrophage accumulation of inhaled gallium-67 citrate in normal lungs.

Injected 67Ga has been used extensively to monitor inflammatory processes in the peripheral lung. We hypothesized that inhaled 67Ga may be useful in marking early airway inflammation in smokers. Eight nonsmokers and eight smokers breathed a 67Ga aerosol and imaging was performed immediately and 24 and 96 hr later. Approximately two-thirds of the initial dose remained in the lungs at 24 hr in both groups and no difference was seen between the groups. Only a very slight decrease was seen in both groups at 96 hr suggesting the gallium becomes bound to lung tissue or to cells not rapidly removed from the lungs. Autoradiography was performed on tissue from two smoke-exposed guinea pigs and two human patients undergoing resection surgery who breathed the gallium aerosol 24 hr prior to tissue removal. Silver grain accumulations were seen only over macrophages. We conclude that macrophage associated accumulation of 67Ga occurs in healthy lungs, and that it is not feasible to use aerosolized gallium to assess airway inflammation in smokers.

Adult↗
PubMed1984

The structure of tight junctions in the tracheal epithelium may not correlate with permeability.

To test the hypothesis that cigarette smoke produces changes in the morphology of tight junctions guinea pigs were exposed to cigarette smoke or air in a previously standardized fashion (Simani et al. 1974). Permeability is greatest one half hour following exposure to cigarette smoke (Hulbert et al. 1981). The animals were sacrificed at that time. The tracheal epithelium was studied using both thin-section and freeze-fracture techniques. A quantitative analysis of the organization and integrity of junctional complexes was performed for each animal. Organization was assessed by measuring and comparing areas delimited by PF fibers and EF furrows. PF fiber integrity was assessed by measuring uninterrupted lengths of fibers and furrows from freeze-fracture replicas. This assessment did not demonstrate a change in tight-junction morphology following exposure to cigarette smoke.

Animals↗
PubMed1983

Ca2+ and pH induced fusion of small unilamellar vesicles consisting of phosphatidylethanolamine and negatively charged phospholipids: a freeze fracture study.

Fusion processes in small (sonicated) unilamellar vesicle (SUV) systems composed of 80 mol % unsaturated phosphatidylethanolamine and 20 mol % of phosphatidylserine, phosphatidylinositol, phosphatidic acid or cardiolipin have been examined by freeze-fracture techniques. All these mixtures have the property that Ca2+ and, in some cases low pH, can trigger bilayer to hexagonal (HII) phase transitions in large multilamellar dispersions of these lipid mixtures. It is shown that when the SUV systems are subjected to similar protocols, the vesicles first fuse to form larger systems prior to HII phase formation and this fusion is accompanied by the appearance of lipidic particle structures, often localized to the fusion interface. We conclude that factors promoting HII phase structure initially result in fusion of unilamellar systems and that this fusion proceeds via intermediary formation of non-lamellar, possibly inverted micellar, structure.

Calcium↗
PubMed1982

An improved method for fixation of the respiratory epithelial surface with the mucous and surfactant layers.

A new technique for the stabilization of the mucous layers in the upper respiratory tree is described. The methodology combines perfusion of the thoracic vasculature through the carotid, thyroid, and bronchial arteries, with aerosolization of fixative onto the airway surface through a tracheostomy. The biphasic nature of the mucous layer in healthy animals is confirmed and is compared with the nature of the mucus in animals exposed to cigarette smoke. The fundamental advantage of the technique is that, because airway surface phenomena are stabilized, more thorough correlates of physiology and morphology can be accomplished. The intrapulmonary airways and parenchyma are also fixed by using this technique, and the results are discussed. A preliminary communication using this technique to document leukocyte transit across the respiratory mucosa has been published.

Aerosols↗
PubMed1981

Airway permeability to horseradish peroxidase in guinea pigs: the repair phase after injury by cigarette smoke.

Airway permeability was examined in the 24-h period immediately after injury by cigarette smoke in 30 guinea pigs studied in groups of five at 30 min and 1, 6, 12, and 24 h after smoke exposure, and in 1 control group. The animals were anesthetized, tracheostomized, a carotid cannula inserted, and purified horseradish peroxidase was instilled on the airway surface via the tracheostomy tube. Blood samples (0.8 ml) were drawn and replaced with heparinized saline before and at 10, 15, 20, 30, and 40 min after horseradish peroxidase instillation. The animals were then killed, and samples of trachea and lung tissue taken for wet/dry wt determinations and for light and electron microscopic examination. The HRP concentrations in the blood were determined using an Elisa plate assay. We found the acute exposure to 100 puffs cigarette smoke resulted in a transient increase in airway epithelial permeability of HRP with a maximum at 30 min and a return to control values by 12 h after insult. These changes in mucosal permeability occurred in relation to a well-defined inflammatory reaction where increased permeability occurred during the exudative phase, which was monitored by measuring airway wet wt/dry wt ratios and the infiltration of polymorphonuclear cells. The return to the control value of permeability was associated with the repair phase of the inflammatory reaction, which was measured by monitoring basal cell mitoses.

Animals↗